fftw2 software package provides library for computing Fast Fourier Transforms, you can install in your Ubuntu 16.04 LTS (Xenial Xerus) by running the commands given below on the terminal,
$ sudo apt-get update $ sudo apt-get install fftw2
fftw2 is installed in your system.
Make ensure the fftw2 package were installed using the commands given below,
$ sudo dpkg-query -l | grep fftw2 *
You will get with fftw2 package name, version, architecture and description in a table
| Distro | Ubuntu 16 04 lts xenial xerus |
| Section | Libraries |
| Package | fftw2 |
| Version | 2.1.5-3 |
| Description | library for computing Fast Fourier Transforms |
| Sub Section | Libs |